Many forms of anterior uveitis are presumed to be caused by autoimmunity directed toward ocular antigens. However, there has been no confirmation that an ocular-specific antigen is involved in this process. It is important to develop an understanding of the mechanisms of inflammation in patients that have anterior uveitis. The presumed site of inflammation in these patients is the iris and ciliary body. Therefore, we began to look for iris- specific proteins to which patients might have an autoimmune response. Patients with anterior uveitis were screened for autoantibodies directed against bovine iris. Antibodies were detected to a protein with a molecular weight of approximately 22,000 in some patients. When compared to a control group, patients, in general, have higher levels of this antibody than do control individuals. Until the protein is isolated and T-cell responses can be measured, the true significance of these antibodies will be unclear. Antibodies to retinal antigens are much less revealing than the corresponding T-cell responses in distinguishing patients from controls. The protein that has been identified appears to be specific to the iris and is not found in other tissues of the body. Purification of this protein for other immunologic studies is in progress.